1. Field of the Invention
This invention relates to power transmission belts/belt sleeves and, more particularly, to a belt/belt sleeve having at least one of a) ribs and b) a plurality of cog teeth thereon. The invention is further directed to a method of making such a power transmission belt/belt sleeve.
2. Background Art
It is known to make power transmission belts by laminating a cushion rubber layer, with at least one embedded, load carrying tension member extending lengthwise of the belt, to a compression rubber layer having longitudinally extending ribs with embedded, laterally extending, short, reinforcing fibers. Commonly, to make such a transmission belt, a continuous sleeve, defined by laminating the cushion rubber layer with the embedded load carrying member to the compression rubber layer, is placed in a vulcanizing assembly. The sleeve surface, in which the ribs are to be formed, is in a flat state during the vulcanization process. At the completion of the vulcanization process, the compression rubber layer is ground to form the ribs. The sleeve is then cut to produce individual belts of a desired width.
With this process, the removed material during the grinding process represents waste, which must be accumulated and appropriately disposed of. In response to this problem, a number of different processes have been developed for forming ribs without the requirement of grinding.
In JP-UM-B-27946/1982 Publication, a process is disclosed wherein an unvulcanized belt sleeve, having the aforementioned joined, compression rubber layer and cushion rubber layer with at least one load carrying member embedded therein, is inserted into a cylindrical metal die assembly. The compression layer resides against an outer, radially inwardly facing mold surface having formed rib grooves thereon. The ribs are formed in the belt sleeve by pressing the compression rubber layer radially outwardly against the ribbed mold surface.
Another process for making belts is disclosed in each of JP-A-40087/1978 and JP-A-25948/1983 Publications. In each of these publications, an unvulcanized belt sleeve is disclosed having an unformed compression rubber layer laminated outside of a cushion rubber layer in which at least one load carrying member is embedded. The unvulcanized belt sleeve is fit around an inner die element which is expandable in a radial direction. The inner die element, with the unvulcanized belt sleeve fit thereto, is placed in an outer die element with a radially inwardly facing surface in which rib grooves are formed. By expanding the diameter of the inner die element, ribs are formed by urging the compression rubber layer radially outwardly into conforming relationship with the grooved, outer die element surface.
In JP-A-86236/1998 Publication, a process is disclosed wherein exposed portions of the ribs, formed as described in the publications in the prior paragraph, are removed by grinding, thereby exposing short fibers embedded in the compression layer.
In Japanese Patent Publication No. 2708717, a process is disclosed wherein endless ribs are formed in the compression rubber layer by extruding the same in a lengthwise direction. The compression rubber layer, with the preformed ribs, is laminated to the cushion rubber layer in which a load carrying cord is embedded. The resulting, unvulcanized belt sleeve is thereafter placed into a die and vulcanized.
In those systems, wherein ribs are formed by forcing an unvulcanized belt sleeve radially against a die surface with rib grooves, as in JP-A-5340087, during this process the cushion rubber layer is likewise deformed in the radial direction. However, because the load carrying member(s) is embedded in the cushion rubber layer, deformation of the load carrying member(s) likewise occurs. A disturbance in the load carrying member(s), such as an undulation in the radial direction, a disturbance of pitch, etc. might occur.
The process disclosed in Japanese Patent Publication No. 2708717 also inherently has some potential drawbacks. Because the ribs are formed through an extrusion process in a lengthwise direction, the rubber in the compression layer may not fill the mold with a uniform density to consistently produce a precise rib shape with a homogeneous composition. That is, the flow of the rubber in the compression layer may not be uniform, particularly in the direction transversely to the length of the belt sleeve/ribs.